This invention relates to peristaltic pumps.
Conventional peristaltic pumps comprise a pumphead housing in which a tube extends. The tube is acted upon by drive means such as a rotor to perform a peristaltic pumping action. The tube extends from the pumphead housing and is provided at its ends with connectors for connection to other equipment.
With such pumps, the tube is gripped by the is housing to ensure that it is held stationary with respect to the housing so that the rotor can act properly upon it. However, when fitting the tube, it is not always easy to ensure that the tension of the tube around the rotor is correct nor that the tube is not twisted or otherwise distorted. Improper installation of the tube can lead to poor pump performance and short tube life, particularly if the pump is operated at high pressure.
In accordance with the present invention there is provided a peristaltic pumphead comprising a pumphead housing accommodating a tube and driving means for causing a peristaltic action in the tube, the tube being provided at each end with locating means for locating the ends of the tube releasably in the pumphead housing to prevent lengthwise displacement of each end of the tube relative to the pumphead housing.
Since the tube ends are precisely located within the pumphead housing, it is possible for the tube, with the locating means, to be supplied in required lengths so that the tension in the tube, after fitting, is correct. The locating means may be provided with fittings to enable the connection of further equipment.
The locating means may take the form of cooperating flanges and recesses provided one on the pumphead and one on the tube. For example, the locating means on the tube may comprise a flange projecting outwardly from the wall of the tube, while the pumphead may have a recess for receiving the flange at each end of the tube. The flange may be non-circular; for example, it may have a flat for engaging a complementary part of the recess. This measure ensures that each end of the tube is installed in a predetermined orientation, so avoiding twisting of the tube on installation. Also, the use of locating means in accordance with the present invention can avoid the need to clamp the tube in order to maintain it in position. Such clamping tends to throttle the flow through the tube, particularly if high pressures are to be maintained.
The locating means may be a close fit with the corresponding formation in the pumphead housing. The pumphead housing may be in two parts, which are brought together to form a sealed enclosure and to clamp the locating means between them in a fluid-tight manner.
The locating means may be provided on an end fitting attached to the tube end, or it may be formed integrally, for example by moulding, on the tube end region. If the locating means is a separate fitting, it may be fitted to the tube end by means of a simple push-fit, or it may be secured to the tube end by swaging.
In most conventional peristaltic pumps, the tube is arranged in a semi-circular arc around a rotor which forms the driving means. The wall of the pumphead housing defines a track within which the tube lies. In a preferred embodiment, the tube has an overall length which is slightly shorter than the combined length of the track and the distances between the ends of the track and the ends of the tube, A consequence of this is that, when installed, the tube is spaced slightly from the track. As a result, the tube is centred more reliably within the track during operation.
A pump in accordance with the present invention may be capable of maintaining relatively high output pressures, for example up to 4 bar.